refactor: avoid unnecessary computation in evaluate_varmap!

Author: AayushSabharwal

src/systems/problem_utils.jl

@@ -450,8 +450,11 @@ in `varmap`, it is ignored.
 """
 function evaluate_varmap!(varmap::AbstractDict, vars; limit = 100)
     for k in vars
+        v = get(varmap, k, nothing)
+        v === nothing && continue
+        symbolic_type(v) == NotSymbolic() && !is_array_of_symbolics(v) && continue
         haskey(varmap, k) || continue
-        varmap[k] = fixpoint_sub(varmap[k], varmap; maxiters = limit)
+        varmap[k] = fixpoint_sub(v, varmap; maxiters = limit)
     end
 end